Process for obtaining cast iron



- auenn PATENT e s,

II'WOMTARSKY, 01's AACHEN, GERMANY, ASSIGNOR TO THE FIRM: VEREINIG'IE STAHLWERKE AKTIENGESELL SCHAFT, OF DUSSELDORF, GERMANY.

, PROGESS'FOR QB TAINING CAST IRON.

Ho Drawingr Application flled June 17, 1927, Serial No. 199,624, and in Germany Junel15, 1928.

The invention has reference to a method of improving the quality of cast-iron.

The applicant has found that the production of'highly valuable cast iron has a close 5 relation to the manner of treating the liquid material before casting. It has been found that following .the disappearance of the graphitic nuclei and of gases in the liquid iron and by subsequently superheating the 0 molten iron the so-called eutectic point of solidification is lowered. In consequence thereof the formation of graphite is effected in rates of temperature of a so-called large spontaneous nucleus-number. This process is again favoured by the formation of a finely graphitic structure in the principal mass of the iron. In addition to a number of white solidified special kinds of iron poor in carbon and silicon and sometimes rich in manganese, several kinds of so-called foundry crude iron are' melted in foundries, such as hematite iron, foundry iron, Luxembourg iron and so on. These kinds are inmost casestrich in silicon and have a gray fracture, that is to say: they are graphitic. On melting such kinds of gray iron in cupola furnaces, re-

verberatory furnaces or electric furnaces, the

graphite separated out goes in solution only with muchdifiiculty or the carbon dissolved is to be found in the liquid solution predominantly in an elementary form. In conse quence thereof the excessive cooling power on solidification of the iron, which has been cast, is decreased by thejmechanical and elementary graphitic nuclei which are present. All iron solidified under these conditions has thus always a coarse-graphitic structure and inferior mechanical and physical qualities. The method of casting iron rich in silicon of the fracture. But it has been found that.

the quality of molten cast, iron is determined not only by the appearance of the fracture, but principally by the chemical composiof meltin 0 'Accordmg to the invention a cast iron of higher q1f1 ality is obtained in the simplest for the foundry-Works in sand-pigs originates tion of the crude iron' and by the conditions the so-called foundryv crude-iron (also hematite, Luxembourg iron etc.)' of the blast 6 moldsflin'steadof in sand. pigs,

applied for hastening the cooling, for instance by sprayingwith water. Alternatively it is possible to cast the liquid iron directly into water. As in this case a considerably higher percentage of the total content of carbon in theiro'n' in the solidified state would be in the form of carbide, the liquid iron obtained on melting this iron in a cupola fur- 1 masoe nace, a reverberatory furnace orin an electric furnace, will consequently contain less mechanical and elementary graphitic nuclei, the carbon going in solution predominantly in the form of carbide. The result of this method is a cast iron ofhigher value with better mechanical and physical qualities.

It .is of special importancefor this invention, that the improvement in the quality of the cast iron can be obtained without any change in the operation-and without special costs. The casting in chill moulds will be advantageous for blast-furnace works, due to the fact that the further operations necessary after the cooling has been effected, will be facilitated, whereas the new process possesses the further advantage for foundries, that an iron is obtained thereby which is free from any depositions of sand, so that smaller 'residues and a smaller quantity of slag will remain in the melting-furnace;

What I claim and desire tosecure by Letters Patent of the United States is:

1. The method of producing high grade cast iron from pig iron of grades which according to existing practice are solidified by casting in sand and exhibit a grey fracture consisting in obtaining a predominantly white solidification by casting in chill molds having a cross-sectional area of less than 100 square centimeters and causing such amounts of graphite as may remain after solidification to be dissolved by remelting at a high temperature. I

2. The method ofproducing high grade cast iron from pig ironof grades which ac-- cording to existing practice are solidified by casting in. sand and exhibit a grey fracture consisting in obtaining a predominantly white solidification by casting in chill molds having a cross-sectional area of less than 100 square centimeters and sprinkling with water and causing such amounts of graphite as may remain after solidification to be dissolved by remelting' at a high temperature.

' seem PIWQWA sKr." 

